Zinc deficiency in growing individuals results in abnormal bone growth. This proposal described the application of two useful approaches to the study of the nutritional effects of zinc deficiency on the formation of bones. The first approach involves the use of a nylon tube implanted into the aveolar cavity of the mandibular incisor of guinea pigs, from which a purely zinc-deficient bone can be obtained in a zinc depleted animal. The second approach is to culture rat calvaria in medium containing either zinc deficient or adequate rat serum, which serves as a convenient alternative for nutritional depletion studies in animal models. The uptake of radioactivity labeled precursors of the components of organic matrix of the bone will then be evaluated in vivo and in vitro. Emphasis will be placed on the metabolism of glycosaminoglycans (GAG's), since GAG's are important components of the organic matric and previous studies indicate that major alterations in GAG composition take place in Zn deficient bones. The effect of zinc on another calcified tissue, the tooth, has received only limited attention. This proposal also describes the use of two model systems (rat teeth and caries models) to examine the effect of zinc deficiency on developing teeth. Attempts will be correlate their structural and biochemical changes with the susceptibility to dental caries. This will be done by challenging zinc deficient rat pups, which are born to and nursed by marginally zinc-deficient rat dams, with Streptococcus mutans and a caries promoting diet.